Two questions:* If the offensive player points the cone at a base in another player's system, but before the challenge resolves said player ends up with a token on said base (making it no longer a place a challenge could have been started) what happens?

* And more of an opinion question: Should seeker and calculator be listed as a too powerful power combination?

I'm inclined to say that if you've moved on from the "point the cone" phase, the offensive player is SOL - if another player's alien power gives the offensive player a base, or if another player plays a card that does so, and the phase is legitimate, that's part of why that power or card exists (i.e., to potentially thwart the offensive player). That's how I'd definitely interpret the rules. In that case, the best bet for the offensive player is a compromise/compromise situation with the defensive player.

And give an example of why Seeker and Calculator would be too powerful a combination.